South Korea says two of four North Korean fishermen who were rescued off a boat drifting in South Korean waters will remain in the country after expressing their desire to defect.

Seoul's Unification Ministry on Tuesday said the two other fishermen were sent back to North Korea through an inter-Korean village.

The defections by the two fishermen come at a delicate time in bilateral relations between the Koreas.

North Korea has significantly reduced its dialogue and engagement with South Korea since February, when a high-stakes nuclear summit between leader Kim Jong Un and U.S. President Donald Trump collapsed over disagreements on exchanging sanctions relief for disarmament.